The Greenland halibut or Greenland turbot (''Reinhardtius hippoglossoides'') belongs to the family

Pleuronectidae Pleuronectidae, also known as righteye flounders, are a family of flounders. They are called "righteye flounders" because most species lie on the sea bottom on their left sides, with both eyes on their right sides. The Paralichthyidae are the op ...

(the right-eye flounders), and is the only species of the genus ''Reinhardtius''. It is a predatory fish that mostly ranges at depths between , and is found in the cold northern Atlantic, northern Pacific, and Arctic Oceans. It has a variety of other English vernacular names, including black halibut, blue halibut, lesser halibut, and Newfoundland turbot; while both Newfoundland turbot and Greenland turbot are in common use in North America (sometimes even without the location, just "turbot"), these names are typically not used in Europe, where they can cause easy confusion with the true turbot (''Scophthalmus maximus''). The Greenland halibut is fished commercially across its range with disputes over the fishing rights for this species in the Atlantic Ocean off Canada resulting in the Turbot War of the mid-1990s (a "war" without any injuries or casualties). The Greenland halibut is a

flatfish A flatfish is a member of the ray-finned demersal fish order Pleuronectiformes, also called the Heterosomata, sometimes classified as a suborder of Perciformes. In many species, both eyes lie on one side of the head, one or the other migrating ...

, and the left eye has migrated during the fish's development so that it is on the right side of the head. However, in this fish, it has not moved as far as in bottom-dwelling flatfish and the fish can probably see forwards. The Greenland halibut can swim in a vertical position and both sides of its body are a speckled brown colour, but the left side is rather paler than the right. The

Hellefisk Fjord Hellefisk Fjord ( da, Hellefiskefjord) is a fjord in Peary Land, northern Greenland. To the northeast, the fjord opens into the Wandel Sea of the Arctic Ocean. This fjord is named after the Greenland halibut ( da, Hellefisk). Geography The Hellefi ...

in Greenland is named after this fish, hellefisk being the Danish name for Greenland halibut.

Description

Its morphology with the left eye positioned on the

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal c ...

ridge of the forehead gives it an appearance of a

cyclops In Greek mythology and later Roman mythology, the Cyclopes ( ; el, Κύκλωπες, ''Kýklōpes'', "Circle-eyes" or "Round-eyes"; singular Cyclops ; , ''Kýklōps'') are giant one-eyed creatures. Three groups of Cyclopes can be distinguish ...

when looking straight at it. The central position of the left eye in the Greenland halibut probably gives it a much wider range of

peripheral vision Peripheral vision, or ''indirect vision'', is vision as it occurs outside the point of fixation, i.e. away from the center of gaze or, when viewed at large angles, in (or out of) the "corner of one's eye". The vast majority of the area in th ...

in comparison to other flatfish, where the eye has migrated completely. Its body shape is elongated and compressed dorsoventrally and muscles on both sides are equally developed. Both sides are pigmented, but the left blind side is slightly lighter in color than the right side. The maximum length is about and the maximum weight is about , the normal length is and they usually weigh .

Distribution and habitat

The Greenland halibut is a cold-water species found at depths from near the surface to , but mainly between . It is mainly found in waters with temperatures from , but has also been observed at subzero temperatures down to . It has a circumpolar distribution in the

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...

and is found in both the North Atlantic and the North Pacific Oceans. In the North Pacific, it ranges from the

Sea of Japan The Sea of Japan is the marginal sea between the Japanese archipelago, Sakhalin, the Korean Peninsula, and the mainland of the Russian Far East. The Japanese archipelago separates the sea from the Pacific Ocean. Like the Mediterranean Sea, i ...

near

Honshu , historically called , is the largest and most populous island of Japan. It is located south of Hokkaidō across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyūshū across the Kanmon Straits. The island s ...

northwards to the

Chukchi Sea Chukchi Sea ( rus, Чуко́тское мо́ре, r=Chukotskoye more, p=tɕʊˈkotskəjə ˈmorʲɪ), sometimes referred to as the Chuuk Sea, Chukotsk Sea or the Sea of Chukotsk, is a marginal sea of the Arctic Ocean. It is bounded on the west ...

, east through the

Aleutian Islands The Aleutian Islands (; ; ale, Unangam Tanangin,”Land of the Aleuts", possibly from Chukchi ''aliat'', "island"), also called the Aleut Islands or Aleutic Islands and known before 1867 as the Catherine Archipelago, are a chain of 14 large v ...

, and south as far as northern

Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...

in Mexico. In the North Atlantic, it occurs from the British Isles to northern Norway, Faroe Islands, Iceland, and eastern Greenland in the east and from

Newfoundland Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...

to northwestern Greenland in the west.

Biology

As a species of

, it is presumed that this fish would be primarily associated with the seabed, however, tagging information shows that they spend time both close to the seabed and with frequent excursions into the water column, presumably for feeding. These movements up into the water column explain why it is often caught pelagically. It has been speculated that when in the water column they will swim in a vertical position, but data from data storage tags do not support this hypothesis. Greenland halibut consumes prey from demersal and pelagic habitats and is primarily a piscivore. It also feeds upon a variety of other prey items such as

amphipods Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far describ ...

and

shrimp Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are ref ...

s. In the north-east Arctic,

squid True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fittin ...

and fish such as

Atlantic herring Atlantic herring (''Clupea harengus'') is a herring in the family Clupeidae. It is one of the most abundant fish species in the world. Atlantic herrings can be found on both sides of the Atlantic Ocean, congregating in large schools. They can ...

capelin The capelin or caplin (''Mallotus villosus'') is a small forage fish of the smelt family found in the North Atlantic, North Pacific and Arctic oceans. In summer, it grazes on dense swarms of plankton at the edge of the ice shelf. Larger capelin ...

and

Atlantic cod The Atlantic cod (''Gadus morhua'') is a benthopelagic fish of the family Gadidae, widely consumed by humans. It is also commercially known as cod or codling. In the Beaufort Sea, polar cod and Gelatinous Snailfish are important prey items while in the shrimp grounds of west Greenland, shrimp and

redfish Redfish is a common name for several species of fish. It is most commonly applied to certain deep-sea rockfish in the genus ''Sebastes'', red drum from the genus '' Sciaenops'' or the reef dwelling snappers in the genus '' Lutjanus''. It is also a ...

are the primary prey. They are known to feed on significant quantities of offal discarded from fishing vessels. Greenland halibut spawn from January–March. During spawning, Greenland halibut will perform spawning rises where they will rise up through the water column from deep water to depths of around 200–350 m where they will release their eggs and sperm before descending back to deeper water. Females will release one batch of eggs each year after while the males will spawn with multiple females over the course of the spawning season. The eggs and larvae remain suspended in the water column throughout development and complete their

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

on attaining a length of Greenland halibut have an unusual form of gonad development in comparison with many other fish species. They will develop two groups of

oocyte An oocyte (, ), oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female ...

s concurrently, one group will be spawned in the current spawning cycle, the other will be spawned in the next spawning cycle. The reason for this is due to the large eggs (2.5-3.0 mm in diameter) and the cold water in which they in habit, it takes more than 1 year for oocytes to complete

vitellogenesis Vitellogenesis is the process of yolk protein formation in the oocytes of non mammalian vertebrates during sexual maturation. The term ''vitellogenesis'' comes from the Latin ''vitellus'' ("egg yolk"). Yolk proteins, such as Lipovitellin and P ...

. If they were to develop one group of oocytes at a time, they would only be able to spawn every two years.

Fishing and conservation

Greenland halibut are fished commercially by several countries including Russia, Norway, Iceland, Germany, Spain, Greenland and Canada and are caught using a variety of gears including bottom trawls, longline and

gillnets Gillnetting is a fishing method that uses gillnets: vertical panels of netting that hang from a line with regularly spaced floaters that hold the line on the surface of the water. The floats are sometimes called "corks" and the line with corks is ...

. Reported landings have been around 50-140 thousand metric tonnes per year since 1960. Fishing is the most important industry in Greenland and Greenland halibut is the second-most important species (after northern prawn), meaning that any changes can have a significant effect on the country's overall economy, as well as the local economy as most inshore fisheries involve small-scale, small-boat fishers. Similarly, the fishery for Greenland halibut is very important to some

First Nations First Nations or first peoples may refer to: * Indigenous peoples, for ethnic groups who are the earliest known inhabitants of an area. Indigenous groups *First Nations is commonly used to describe some Indigenous groups including: **First Natio ...

and

Inuit Inuit (; iu, ᐃᓄᐃᑦ 'the people', singular: Inuk, , dual: Inuuk, ) are a group of culturally similar indigenous peoples inhabiting the Arctic and subarctic regions of Greenland, Labrador, Quebec, Nunavut, the Northwest Territorie ...

communities in Canada. The species is not threatened overall and it can be locally abundant, but it is

near threatened A near-threatened species is a species which has been categorized as "Near Threatened" (NT) by the International Union for Conservation of Nature as that may be vulnerable to endangerment in the near future, but it does not currently qualify fo ...

. Until the 1970s, the species declined due to overfishing, but since the 1980s, an overall slight increase has been seen, although some local populations have further declined. The primary threat is

overfishing Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in t ...

.Secondary threats are related to their deep-water spawning grounds. Some are in areas with oil and gas extraction. Others spawning grounds are in deep near-shore regions where the ecosystem relies on nutrients from meltwater from

glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such a ...

s, but these are gradually disappearing. In 2010, Greenpeace International added the Greenland halibut to its seafood red list because some fishing for the Greenland halibut is by

bottom trawl Bottom trawling is trawling (towing a trawl, which is a fishing net) along the seafloor. It is also referred to as "dragging". The scientific community divides bottom trawling into benthic trawling and demersal trawling. Benthic trawling is tow ...

, which can cause significant environmental damage, and some populations appear to be overfished. In coastal regions and some offshore regions, fishing for Greenland halibut mainly is done by deep-sea

long line fishing Longline fishing, or longlining, is a commercial fishing angling technique that uses a long ''main line'' with baited hooks attached at intervals via short branch lines called ''snoods'' or ''gangions''.gillnet Gillnetting is a fishing method that uses gillnets: vertical panels of netting that hang from a line with regularly spaced floaters that hold the line on the surface of the water. The floats are sometimes called "corks" and the line with corks is ...

s, which does not cause the same damage as bottom trawling. In 2017, the

Marine Stewardship Council The Marine Stewardship Council (MSC) is a non-profit organization which aims to set standards for sustainable fishing. Fisheries that wish to demonstrate they are well-managed and sustainable compared to the MSC's standards are assessed by a t ...

certified that the fishery for Greenland halibut was sustainable. Because Canada and Greenland share the offshore populations in the

Davis Strait Davis Strait is a northern arm of the Atlantic Ocean that lies north of the Labrador Sea. It lies between mid-western Greenland and Baffin Island in Nunavut, Canada. To the north is Baffin Bay. The strait was named for the English explorer John ...

–

Baffin Bay Baffin Bay (Inuktitut: ''Saknirutiak Imanga''; kl, Avannaata Imaa; french: Baie de Baffin), located between Baffin Island and the west coast of Greenland, is defined by the International Hydrographic Organization as a marginal sea of the Arc ...

region in between them, the two have shared the

fishing quota Catch share is a fishery management system that allocates a secure privilege to harvest a specific area or percentage of a fishery's total catch to individuals, communities, or associations. Examples of catch shares are individual transferable quot ...

and follow the same guidelines in this region. Offshore populations in this region are healthy, stable and well-managed, but in more coastal areas some populations have fallen due to overfishing, although they do get a regular input of young fish from the stable offshore populations. Deals on fishing quotas for offshore fishing for Greenland halibut and other species have also been reached between Greenland, Faroe Islands, Norway, and Russia. Among well-monitored populations, the ones in the East Greenland–Iceland region (i.e.,

Greenland Sea The Greenland Sea is a body of water that borders Greenland to the west, the Svalbard archipelago to the east, Fram Strait and the Arctic Ocean to the north, and the Norwegian Sea and Iceland to the south. The Greenland Sea is often defined a ...

Denmark Strait The Denmark Strait () or Greenland Strait ( , 'Greenland Sound') is an oceanic strait between Greenland to its northwest and Iceland to its southeast. The Norwegian island of Jan Mayen lies northeast of the strait. Geography The strait connect ...

and nearby) experienced the greatest decline since the 1970s. In 2019, the parties agreed on a reduction of fishing for Greenland halibut in the Greenland Sea region, following recommendations by biologists. In some inshore waters of Greenland, fishing quotas for Greenland halibut have been temporarily raised several times, contrary to recommendations by fisheries biologists, and leading to recommendations of a clearer separation of decisions on quotas and the Greenlandic Government (decisions not fully left to Greenland's Fisheries Commission). A smaller fishery for the species also exists in the

Gulf of Alaska The Gulf of Alaska (Tlingit: ''Yéil T'ooch’'') is an arm of the Pacific Ocean defined by the curve of the southern coast of Alaska, stretching from the Alaska Peninsula and Kodiak Island in the west to the Alexander Archipelago in the east ...

(where relatively uncommon) and the

Bering Sea The Bering Sea (, ; rus, Бе́рингово мо́ре, r=Béringovo móre) is a marginal sea of the Northern Pacific Ocean. It forms, along with the Bering Strait, the divide between the two largest landmasses on Earth: Eurasia and The Am ...

region (where more common), and these populations are not overfished. The oil-rich, soft meat is regarded as good, but inferior to that of the

Atlantic halibut The Atlantic halibut (''Hippoglossus hippoglossus'') is a flatfish of the family Pleuronectidae. They are demersal fish living on or near sand, gravel or clay bottoms at depths of between . The halibut is among the largest teleost (bony) fish in ...

and European turbot. Traditionally, it was salted, but today it is mostly

smoked Smoking is the process of flavoring, browning, cooking, or preserving food by exposing it to smoke from burning or smoldering material, most often wood. Meat, fish, and '' lapsang souchong'' tea are often smoked. In Europe, alder is the tra ...

or frozen and the primary market is in East Asia, where it is regarded as a delicacy. However, because of the thick skin, high fat content, and low meat yield, as much as one-third of the fish can be lost in production. In Greenland, the remains are often used as food for the

sled dog A sled dog is a dog trained and used to pull a land vehicle in harness, most commonly a sled over snow. Sled dogs have been used in the Arctic for at least 8,000 years and, along with watercraft, were the only transportation in Arctic areas ...

s ( Greenland dogs).

References

{{Taxonbar, from=Q1466948 Greenland halibut Fauna of Greenland Commercial fish Fish of the Arctic Ocean Fish of the North Atlantic Greenland halibut Taxa named by Johann Julius Walbaum Taxobox binomials not recognized by IUCN